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Merge "Move encrypted directories into place already-encrypted" am: ec6e52aadc am: 01ca68c4f8

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Original change: https://android-review.googlesource.com/c/platform/system/vold/+/2620092

Change-Id: Ib6627057ba9d1a11fc3ca2f7dbdc53254a4bf35f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
This commit is contained in:
Eric Biggers 2023-06-13 23:21:11 +00:00 committed by Automerger Merge Worker
commit 8e38d39179
1 changed files with 31 additions and 2 deletions
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33
FsCrypt.cpp
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@ -323,8 +323,37 @@ static bool prepare_dir(const std::string& dir, mode_t mode, uid_t uid, gid_t gi
// Prepare a directory and assign it the given encryption policy.
static bool prepare_dir_with_policy(const std::string& dir, mode_t mode, uid_t uid, gid_t gid,
const EncryptionPolicy& policy) {
if (!prepare_dir(dir, mode, uid, gid)) return false;
if (IsFbeEnabled() && !EnsurePolicy(policy, dir)) return false;
if (android::vold::pathExists(dir)) {
if (!prepare_dir(dir, mode, uid, gid)) return false;
if (IsFbeEnabled() && !EnsurePolicy(policy, dir)) return false;
} else {
// If the directory does not yet exist, then create it under a temporary name, and only move
// it to the final name after it is fully prepared with an encryption policy and the desired
// file permissions. This prevents the directory from being accessed before it is ready.
//
// Note: this relies on the SELinux file_contexts assigning the same type to the file path
// with the ".new" suffix as to the file path without the ".new" suffix.
const std::string tmp_dir = dir + ".new";
if (android::vold::pathExists(tmp_dir)) {
android::vold::DeleteDirContentsAndDir(tmp_dir);
}
if (!prepare_dir(tmp_dir, mode, uid, gid)) return false;
if (IsFbeEnabled() && !EnsurePolicy(policy, tmp_dir)) return false;
// On some buggy kernels, renaming a directory that is both encrypted and case-insensitive
// fails in some specific circumstances. Unfortunately, these circumstances happen here
// when processing the "media" directory. This was already fixed by kernel commit
// https://git.kernel.org/linus/b5639bb4313b9d45 ('f2fs: don't use casefolded comparison for
// "." and ".."'). But to support kernels that lack that fix, we use the below workaround.
// It bypasses the bug by making the encryption key of tmp_dir be loaded before the rename.
android::vold::pathExists(tmp_dir + "/subdir");
if (rename(tmp_dir.c_str(), dir.c_str()) != 0) {
PLOG(ERROR) << "Failed to rename " << tmp_dir << " to " << dir;
return false;
}
}
return true;
}